Lubricants with improved low-temperature fuel economy

ABSTRACT

Lubricating oil compositions, formulated to a preselected viscosity grade that demonstrate stay-in-grade capability in a diesel injector shear stability test, are provided. The compositions comprise a major amount of a base oil of lubricating viscosity and a minor amount of (i) a viscosity modifier (VM) or mixtures thereof having a low shear stability index (SSI) and (ii) a VM or mixtures thereof having an SSI greater than that of the VM from (i).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/554,140 filed on Nov. 1, 2011, which is incorporated herein inits entirety by reference.

FIELD

The present disclosure is directed to lubricating oil compositions foruse in crankcase engine oils. More specifically, the disclosure isdirected to crankcase engine oils that are effective in achievingimproved low temperature fuel economy (FE) while simultaneously havinghigh temperature, high shear viscosity (HTHS).

BACKGROUND

Lubricating oil compositions for use as crankcase engine oils comprise amajor amount of a base oil and minor amounts of additives selected toenhance the performance characteristics of the base oil. For example, animportant property of a lubricating oil is its ability to maintain alubricating film between moving mechanical parts over a range oftemperatures. This ability is a function of the viscometric propertiesof the lubricating oil. Typically, oil soluble, high molecular weightpolymers are used to improve the viscometric performance of engine oilcompositions. These materials commonly are referred to as viscositymodifiers (VM), and they function to reduce a decrease in thelubricating composition's viscosity upon an increase in temperature andthe converse upon a decrease in temperature. Indeed, VMs are used toformulate lubricating compositions that meet the multigrade viscosityclassification system of the Society of Automotive Engineers (SAE J300specification) and are numerically numbered such as SAE 0W-20, 0W-30,5W-30, 10W-30, 10W-40 and the like. In this system, the first number isrelated to a low temperature viscosity characteristic, and the secondnumber, to high temperature viscosity characteristics.

It is well known that engine oils having low viscosities at lowtemperatures have desirable low temperature fuel economy (FE)performance. Unfortunately, lowering an engine oil viscosity candetrimentally affect high temperature performance. For example, a loweroil viscosity can result in lower film thickness as measured by hightemperature, high shear (HTHS) viscosity, which is undesirable. Also,the use of VMs to improve the high temperature viscosity of thelubricating composition generally has an adverse affect on the lowtemperature properties.

One object of the present disclosure is to provide lubricating oilcompositions that have improved low temperature FE performance.

Another object of the disclosure is to provide lubricating compositionsfor both gasoline and diesel engines that are effective over a broadrange of lubricant viscosity and that they stay in grade as demonstratedby a diesel injector shear stability test.

Other objectives will become apparent from the detailed description thatfollows.

SUMMARY

One embodiment of the disclosure provides a lubricating oil compositionformulated to a preselected SAE engine oil viscosity grade, saidcomposition comprising:

-   -   (a) a major amount of a base oil of lubricating viscosity; and    -   (b) a minor amount of        -   (i) a viscosity modifier (VM) or mixtures thereof having a            low shear stability index (SSI), and        -   (ii) a VM or mixtures thereof having an SSI greater than the            VM from (i);    -   (c) wherein the sheared kinematic viscosity at 100° C. of the        composition after 90 cycles in the diesel injector shear        stability test (ASTM D7109) is equal to or greater than the        minimum viscosity for the preselected grade before shearing; and    -   (d) wherein the sheared viscosity (c) is less than 20% lower        relative to the unsheared composition viscosity.

In a preferred embodiment of the disclosure, the weight ratios of VM(ii) to VM (i) above, VM(ii)/VM(i), is in the range of from 0.01 to 1.5.

Another embodiment of the disclosure provides a method for lubricatingan internal combustion engine comprising supplying the engine crankcasewith the above lubricant composition whereby the composition is appliedto the engine during operating conditions.

Other embodiments will become apparent from the detailed description andexamples which follow.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art.

It has now been found that an engine oil lubricant compositioncomprising a major amount of base oil and an effective amount of amixture of high-SSI and low-SSI polymeric viscosity modifiers providesimproved fuel efficiency while providing stay-in-grade viscosityretention for stable engine performance.

A wide range of lubricating base oils is known in the art. Lubricatingbase oils that are useful in the present disclosure are both naturaloils, and synthetic oils, and unconventional oils (or mixtures thereof)can be used unrefined, refined, or rerefined (the latter is also knownas reclaimed or reprocessed oil). Unrefined oils are those obtaineddirectly from a natural or synthetic source and used without addedpurification. These include shale oil obtained directly from retortingoperations, petroleum oil obtained directly from primary distillation,and ester oil obtained directly from an esterification process. Refinedoils are similar to the oils discussed for unrefined oils except refinedoils are subjected to one or more purification steps to improve at leastone lubricating oil property. One skilled in the art is familiar withmany purification processes. These processes include solvent extraction,secondary distillation, acid extraction, base extraction, filtration,and percolation. Rerefined oils are obtained by processes analogous torefined oils but using an oil that has been previously used.

Groups I, II, III, IV and V are broad categories of base oil stocksdeveloped and defined by the American Petroleum Institute (APIPublication 1509; www.API.org) to create guidelines for lubricant baseoils. Group I base stocks generally have a viscosity index of between 80to 120 and contain greater than 0.03% sulfur and/or less than 90%saturates. Group II base stocks generally have a viscosity index ofbetween 80 to 120, and contain less than or equal to 0.03% sulfur andgreater than or equal to 90% saturates. Group III stocks generally havea viscosity index greater than 120 and contain less than or equal to0.03% sulfur and greater than 90% saturates. Group IV includespolyalphaolefins (PAO). Group V base stock includes base stocks notincluded in Groups I-IV. The table below summarizes properties of eachof these five groups.

Base Oil Properties

Saturates Sulfur Viscosity Index Group I <90 &/or >0.03% & ≧80 & < 120Group II ≧90 & ≦0.03% & ≧80 & < 120 Group III ≧90 & ≦0.03% & ≧120 GroupIV Includes polyalphaolefins (PAO) Group V All other base oil stocks notincluded in Groups I, II, III, or IV

Natural oils include animal oils, vegetable oils (castor oil and lardoil, for example), and mineral oils. Animal and vegetable oilspossessing favorable thermal oxidative stability can be used. Of thenatural oils, mineral oils are preferred. Mineral oils vary widely as totheir crude source, for example, as to whether they are paraffinic,naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal orshale are also useful. Natural oils vary also as to the method used fortheir production and purification, for example, their distillation rangeand whether they are straight run or cracked, hydrorefined, or solventextracted.

Group II and/or Group II hydroprocessed or hydrocracked basestocks,including synthetic oils such as polyalphaolefins, alkyl aromatics andsynthetic esters are also well known basestock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oilssuch as polymerized and interpolymerized olefins (polybutylenes,polypropylenes, propylene isobutylene copolymers, ethylene-olefincopolymers, and ethylene-alphaolefin copolymers, for example).Polyalphaolefin (PAO) oil base stocks are commonly used synthetichydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄olefins or mixtures thereof may be utilized. See U.S. Pat. Nos.4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are knownmaterials and generally available on a major commercial scale fromsuppliers such as ExxonMobil Chemical Company, Chevron Phillips ChemicalCompany, BP, and others, typically vary from 250 to 3,000, althoughPAO's may be made in viscosities up to 100 cSt (100° C.). The PAOs aretypically comprised of relatively low molecular weight hydrogenatedpolymers or oligomers of alphaolefins which include, but are not limitedto, C₂ to C₃₂ alphaolefins with the C₈ to C₁₆ alphaolefins, such as1-octene, 1-decene, 1-dodecene and the like, being preferred. Thepreferred polyalphaolefins are poly-1-octene, poly-1-decene andpoly-1-dodecene and mixtures thereof and mixed olefin-derivedpolyolefins. However, the dimers of higher olefins in the range of C₁₄to C₁₈ may be used to provide low viscosity basestocks of acceptably lowvolatility. Depending on the viscosity grade and the starting oligomer,the PAOs may be predominantly trimers and tetramers of the startingolefins, with minor amounts of the higher oligomers, having a viscosityrange of 1.5 to 12 cSt.

The PAO fluids may be conveniently made by the polymerization of analphaolefin in the presence of a polymerization catalyst such as theFriedel-Crafts catalysts including, for example, aluminum trichloride,boron trifluoride or complexes of boron trifluoride with water, alcoholssuch as ethanol, propanol or butanol, carboxylic acids or esters such asethyl acetate or ethyl propionate. For example the methods disclosed byU.S. Pat. No. 4,149,178 or U.S. Pat. No. 3,382,291 may be convenientlyused herein. Other descriptions of PAO synthesis are found in thefollowing U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930;4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487.The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No.4,218,330.

The hydrocarbyl aromatics can be used as base oil or base oil componentand can be any hydrocarbyl molecule that contains at least 5% of itsweight derived from an aromatic moiety such as a benzenoid moiety ornaphthenoid moiety, or their derivatives. These hydrocarbyl aromaticsinclude alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkylnaphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylatedthiodiphenol, and the like. The aromatic can be mono-alkylated,dialkylated, polyalkylated, and the like. The aromatic can be mono- orpoly-functionalized. The hydrocarbyl groups can also be comprised ofmixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups,cycloalkenyl groups and other related hydrocarbyl groups. Thehydrocarbyl groups can range from C₆ up to C₆₀ with a range of C₈ to C₂₀often being preferred. A mixture of hydrocarbyl groups is oftenpreferred, and up to three such substituents may be present. Thehydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogencontaining substituents. The aromatic group can also be derived fromnatural (petroleum) sources, provided at least 5% of the molecule iscomprised of an above-type aromatic moiety. Viscosities at 100° C. ofapproximately 3 cSt to 50 cSt are preferred, with viscosities ofapproximately 3.4 cSt to 20 cSt often being more preferred for thehydrocarbyl aromatic component. In one embodiment, an alkyl naphthalenewhere the alkyl group is primarily comprised of 1-hexadecene is used.Other alkylates of aromatics can be advantageously used. Naphthalene ormethyl naphthalene, for example, can be alkylated with olefins such asoctene, decene, dodecene, tetradecene or higher, mixtures of similarolefins, and the like. Useful concentrations of hydrocarbyl aromatic ina lubricant oil composition can be 2% to 25%, preferably 4% to 20%, andmore preferably 4% to 15%, depending on the application.

Esters comprise a useful base stock. Additive solvency and sealcompatibility characteristics may be secured by the use of esters suchas the esters of dibasic acids with monoalkanols and the polyol estersof monocarboxylic acids. Esters of the former type include, for example,the esters of dicarboxylic acids such as phthalic acid, succinic acid,alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid,suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic aciddimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc.,with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types ofesters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexylfumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained byreacting one or more polyhydric alcohols, preferably the hinderedpolyols (such as the neopentyl polyols, e.g., neopentyl glycol,trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylolpropane, pentaerythritol and dipenta-erythritol) with alkanoic acidscontaining at least 4 carbon atoms, preferably C₅ to C₃₀ acids such assaturated straight chain fatty acids including caprylic acid, capricacid, lauric acid, myristic acid, paimitic acid, stearic acid, arachicacid, and behenic acid, or the corresponding branched chain fatty acidsor unsaturated fatty acids such as oleic acid, or mixtures of any ofthese materials.

Suitable synthetic ester components include the esters of trimethylolpropane, trimethylol butane, trimethylol ethane, pentaerythritol and/ordipenta-erythritol with one or more monocarboxylic acids containing from5 to 10 carbon atoms. These esters are widely available commercially,for example, the Mobil P-41 and P-51 esters of ExxonMobil ChemicalCompany).

Other useful fluids of lubricating viscosity include non-conventional orunconventional base stocks that have been processed, preferablycatalytically, or synthesized to provide high performance lubricationcharacteristics.

Non-conventional or unconventional base stocks/base oils include one ormore of a mixture of base stock(s) derived from one or moreGas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate basestock(s) derived from natural wax or waxy feeds, mineral and ornon-mineral oil waxy feed stocks such as slack waxes, natural waxes, andwaxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxyraffinate, hydrocrackate, thermal crackates, or other mineral, mineraloil, or even non-petroleum oil derived waxy materials such as waxymaterials received from coal liquefaction or shale oil orFischer-Tropsch processes, and mixtures of such base stocks.

The lubricating oil compositions of the disclosure comprise a majoramount of a base oil of lubricating viscosity. In general, the base oilwill comprise greater than 50 wt % based on the total weight of thecomposition, and typically, from 50 wt % to 99 wt %, and preferably,from 70 wt % to 95 wt %. The base oil may be selected from any of thesynthetic or natural oils typically used as crankcase lubricating oilsfor spark-ignited and compression-ignited engines. For example, suitablebase oils may comprise one or more base stocks selected from Group III,Group IV and mixtures of Group III and Group IV base stocks. These basestock groups are defined in the American Petroleum Institute Publication“Engine Oil Licensing and Certification System”, Fourteenth Edition,December 1966, Addendum I, December 1998. The base stock typically willhave a kinematic viscosity (KV) at 100° C., as determined by ASTM D445,of 1 cSt to 12 cSt (or mm²/s) and preferably 1.5 cSt to 9 cSt (ormm²/s). Mixtures of synthetic and natural base oils may be used ifdesired.

The compositions of the disclosure include a minor, but effective,amount of a mixture of VMs comprising (i) a VM or mixture of VMs, eachhaving an SSI of 12 or less and (ii) a VM or mixture of VMs, each havingan SSI greater than the VM of (i). In general, the VMs of (i) above willhave SSIs in the range of 4 to 12, and preferably from 4 to 10, whilethe VMs of (ii) above will have SSIs in the range of 8 or higher,preferably from 12 to 65, and may include embodiments of VMs with SSIsof 24 or higher, 35 or higher, 45 or higher, and 50 or higher, forexample.

The amount of the mixture of VMs (i) and (ii) in the composition mayrange from 0.01 wt % to 4 wt %, preferably from 0.01 wt % to 2 wt %, andmore preferably from 0.1 wt % to 2 wt % on a solid polymer basis, basedon the total weight of the composition.

Importantly, the weight ratio of VM(ii)/VM(i) is from 0.01 to 1.5,preferably 0.05 to 1, and more preferably 0.05 to 0.8, and in furtherinstances in the range of 0.1 to 0.8.

For the purposes of this disclosure, the VMs are selected from oilsoluble or oil dispersible polymers typically used in crankcaselubricant compositions to improve the viscometric performance of theengine oil. Viscosity modifiers (VMs) are also known as VI improvers,viscosity index improvers, viscosity improvers, and thickeners.

Suitable viscosity index improvers include high molecular weighthydrocarbons, polyesters and viscosity index improver dispersants thatfunction as both a viscosity index improver and a dispersant. Typicalmolecular weights of these polymers are between 10,000 to 1,000,000,more typically 20,000 to 500,000, and even more typically between 50,000and 200,000.

Examples of suitable viscosity index improvers are linear or star-shapedpolymers and copolymers of methacrylate, butadiene, olefins, oralkylated styrenes. Polyisobutylene is a commonly used viscosity indeximprover. Another suitable viscosity index improver is polymethacrylate(copolymers of various chain length alkyl methacrylates, for example),some formulations of which also serve as pour point depressants. Othersuitable viscosity index improvers include copolymers of ethylene andpropylene, copolymers of olefins and alpha-olefins, hydrogenated blockcopolymers of styrene and isoprene, and polyacrylates (copolymers ofvarious chain length acrylates, for example). Specific examples includestyrene-isoprene or styrene-butadiene based polymers of 50,000 to200,000 molecular weight.

Olefin copolymers, are commercially available from Chevron OroniteCompany LLC under the trade designation “PARATONE®” (such as “PARATONE®8921”, “PARATONE® 8941”, “PARATONE® 8451”, “PARATONE® 68530”); fromAfton Chemical Corporation under the trade designation “HiTEC®” (such as“HiTEC® 5850B”; and from The Lubrizol Corporation under the tradedesignation “Lubrizol® 7067C”. Polyisoprene polymers are commerciallyavailable from Infineum International Limited, e.g. under the tradedesignation “SV200”; diene-styrene copolymers are commercially availablefrom Infineum International Limited, e.g. under the trade designation“SV260”. Other examples include “SV140”, “SV150”, “SV250”, “SV270”, and“SV300”.

The compositions of the disclosure are formulated to meet any one of theSAE viscosity grades for engine oils such as xW-50, xW-40, xW-30, xW-20and the like, where x==15, 10, 5, or 0 and the like, and includes higherviscosity grades and lower viscosity grades, and includes grades notclassifiable by SAE J300.

Compositions according to the disclosure are characterized by the factthat for any preselected viscosity grade, the sheared kinematicviscosity at 10° C. after 90 cycles in the diesel injector shearedstability test ASTM D) 7109 is equal to or greater than the minimumviscosity (at 100° C.) for the preselected grade before shearing.Retention of kinematic viscosity at 100° C. within a single SAEviscosity grade classification by a fresh oil and its sheared version isevidence of an oil's stay-in-grade capability.

The compositions of the disclosure display stay-in-grade capability, anddisplay a viscosity loss measured at 100° C. after 90 cycles in thediesel injector shear stability test of less than 25%, preferably lessthan 20%, more preferably less than 18%, and in some instances less than14%.

The compositions of the present disclosure may also include otheradditives to improve or impart desired properties of the fullyformulated compositions. These additives may be selected fromconventional types of lubricant additives. Such additives includeoxidation inhibitors, dispersants, detergents, corrosion inhibitors,metal deactivators, antiwear additives, extreme pressure additives, pourpoint depressants, seal compatibility agents, friction modifiers,defoamants and dyes. Each of these types of additives may be used inamounts commonly used in lubricant compositions. In general, on anactive ingredient basis, the various lubricant additives will comprisefrom 0.5 wt % to 25 wt %, and preferably, from 2 wt % to 15 wt % basedon the total weight of the composition.

While there are many different types of antiwear additives, for severaldecades the principal antiwear additive for internal combustion enginecrankcase oils is a metal alkylthiophosphate and more particularly ametal dialkyldithiophosphate in which the metal constituent is zinc, orzinc dialkyldithiophosphate (ZDDP). ZDDP can be primary, secondary ormixtures thereof. ZDDP compounds generally are of the formulaZn[SP(S)(OR¹)(OR²)]₂ where R¹ and R² are C₁-C₁₈ alkyl groups, preferablyC₂-C₁₂ alkyl groups. These alkyl groups may be straight chain orbranched. The ZDDP is typically used in amounts of from 0.4 to 1.4 wt %of the total lubricant oil composition, although more or less can oftenbe used advantageously. Preferably, the ZDDP is a secondary ZDDP andpresent in an amount of from 0.6 to 1.0 wt % of the total lubricantcomposition.

Preferable zinc dithiophosphates which are commercially availableinclude secondary zinc dithiophosphates such as those available from forexample, The Lubrizol Corporation under the trade designations “LZ677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite underthe trade designation “OLOA 262” and from for example Afton Chemicalunder the trade designation “HITEC 7169”.

Additional types of antiwear additives are effectively used in lubricantcompositions and include, for example, metal-free, ashless,low-phosphorous, non-phosphorous, oligomeric, polymeric,zinc-containing, metal-containing (other than zinc), multi-functionalchemical combinations of these, and other antiwear additives. Allantiwear additives above, and the like, may be used individually and incombinations in lubricant compositions.

During engine operation, oil-insoluble oxidation byproducts areproduced. Dispersants help keep these byproducts in solution, thusdiminishing their deposition on metal surfaces. Dispersants may beashless or ash-forming in nature. Preferably, the dispersant is ashless.So-called ashless dispersants are organic materials that formsubstantially no ash upon combustion. For example, non-metal-containingor borated metal-free dispersants are considered ashless. In contrast,metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to arelatively high molecular weight hydrocarbon chain. The polar grouptypically contains at least one element of nitrogen, oxygen, orphosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

Chemically, many dispersants may be characterized as phenates,sulfonates, sulfurized phenates, salicylates, naphthenates, stearates,carbamates, thiocarbamates, phosphorous derivatives. A particularlyuseful class of dispersants are the alkenylsuccinic derivatives,typically produced by the reaction of a long chain substituted alkenylsuccinic compound, usually a substituted succinic anhydride, with apolyhydroxy or polyamino compound. The long chain group constituting theoleophilic portion of the molecule which confers solubility in the oilis normally a polyisobutylene group. Many examples of this type ofdispersant are well known commercially and in the literature. ExemplaryU.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892;3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607;3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types ofdispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107;3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347;3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658;3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082;5,705,458. A further description of dispersants may be found, forexample, in European Patent Application No. 471 071, to which referenceis made for this purpose.

Hydrocarbyl-substituted succinic acid compounds are popular dispersants.In particular, succinimide, succinate esters, or succinate ester amidesprepared by the reaction of a hydrocarbon-substituted succinic acidcompound preferably having at least 50 carbon atoms in the hydrocarbonsubstituent, with at least one equivalent of an alkylene amine areparticularly useful.

Succinimides are formed by the condensation reaction between alkenylsuccinic anhydrides and amines. Molar ratios can vary depending on thepoly-amine. For example, the molar ratio of alkenyl succinic anhydrideto TEPA can vary from 1:1 to 5:1. Representative examples are shown inU.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670;and 3,652,616, 3,948,800; and Canada Pat. No. 1,094,044.

Succinate esters are formed by the condensation reaction between alkenylsuccinic anhydrides and alcohols or polyols. Molar ratios can varydepending on the alcohol or polyol used. For example, the condensationproduct of an alkenyl succinic anhydride and pentaerythritol is a usefuldispersant.

Succinate ester amides are formed by condensation reaction betweenalkenyl succinic anhydrides and alkanol amines. For example, suitablealkanol amines include ethoxylated polyalkylpolyamines, propoxylatedpolyalkylpolyamines and polyalkenyipolyamines such as polyethylenepolyamines. One example is propoxylated hexamethylenediamine.Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the alkenyl succinic anhydrides used in thepreceding paragraphs will typically range between 800 and 2,500. Theabove products can be post-reacted with various reagents such as sulfur,oxygen, formaldehyde, carboxylic acids such as oleic acid, and boroncompounds such as borate esters or highly borated dispersants. Thedispersants can be borated with from 0.1 to 5 moles of boron per mole ofdispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols,formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which isincorporated herein by reference. Process aids and catalysts, such asoleic acid and sulfonic acids, can also be part of the reaction mixture.Molecular weights of the alkylphenols range from 800 to 2,500.Representative examples are shown in U.S. Pat. Nos. 3,697,574;3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannichcondensation products useful in this disclosure can be prepared fromhigh molecular weight alkyl-substituted hydroxyaromatics or HN(R)₂group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are wellknown to one skilled in the art; see, for example, U.S. Pat. Nos.3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides,including those derivatives from mono-succinimides, bis-succinimides,and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbylsuccinimide is derived from a hydrocarbylene group such aspolyisobutylene having a Mn of from 500 to 5000 or a mixture of suchhydrocarbylene groups. Other preferred dispersants include succinicacid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts,their capped derivatives, and other related components. Such additivesmay be used in an amount of 0.1 to 20 wt %, preferably 0.5 to 8 wt %.

Detergents are commonly used in lubricating compositions. A typicaldetergent is an anionic material that contains a long chain hydrophobicportion of the molecule and a smaller anionic or oleophobic hydrophilicportion of the molecule. The anionic portion of the detergent istypically derived from an organic acid such as a sulfur acid, carboxylicacid, phosphorous acid, phenol, or mixtures thereof. The counterion istypically an alkaline earth or alkali metal.

Salts that contain a substantially stoichiometric amount of the metalare described as neutral salts and have a total base number (TBN, asmeasured by ASTM D2896) of from 0 to 80. Many compositions areoverbased, containing large amounts of a metal base that is achieved byreacting an excess of a metal compound (a metal hydroxide or oxide, forexample) with an acidic gas (such as carbon dioxide). Useful detergentscan be neutral, mildly overbased, or highly overbased.

It is desirable for at least some detergent to be overbased. Overbaseddetergents help neutralize acidic impurities produced by the combustionprocess and become entrapped in the oil. Typically, the overbasedmaterial has a ratio of metallic ion to anionic portion of the detergentof 1.05:1 to 50:1 on an equivalent basis. More preferably, the ratio isfrom 4:1 to 25:1. The resulting detergent is an overbased detergent thatwill typically have a TBN of 150 or higher, often 250 to 450 or more.Preferably, the overbasing cation is sodium, calcium, or magnesium. Amixture of detergents of differing TBN can be used in the presentdisclosure.

Preferred detergents include the alkali or alkaline earth metal salts ofsulfonates, phenates, carboxylates, phosphates, and salicylates.

Sulfonates may be prepared from sulfonic acids that are typicallyobtained by sulfonation of alkyl substituted aromatic hydrocarbons.Hydrocarbon examples include those obtained by alkylating benzene,toluene, xylene, naphthalene, biphenyl and their halogenated derivatives(chlorobenzene, chlorotoluene, and chloronaphthalene, for example). Thealkylating agents typically have 3 to 70 carbon atoms. The alkarylsulfonates typically contain 9 to 80 carbon or more carbon atoms, moretypically from 6 to 60 carbon atoms.

Klamann in “Lubricants and Related Products”, op cit discloses a numberof overbased metal salts of various sulfonic acids which are useful asdetergents and dispersants in lubricants. The book entitled “LubricantAdditives”, C. V. Smallheer and R. K. Smith, published by theLezius-Hiles Co. of Cleveland, Ohio (1967), similarly discloses a numberof overbased sulfonates that are useful as dispersants/detergents.

Alkaline earth phenates are another useful class of detergent. Thesedetergents can be made by reacting alkaline earth metal hydroxide oroxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with analkyl phenol or sulfurized alkylphenol. Useful alkyl groups includestraight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀.Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol,nonylphenol, dodecyl phenol, and the like. It should be noted thatstarting alkylphenols may contain more than one alkyl substituent thatare each independently straight chain or branched. When a non-sulfurizedalkylphenol is used, the sulfurized product may be obtained by methodswell known in the art. These methods include heating a mixture ofalkylphenol and sulfurizing agent (including elemental sulfur, sulfurhalides such as sulfur dichloride, and the like) and then reacting thesulfurized phenol with an alkaline earth metal base.

Metal salts of carboxylic acids are also useful as detergents. Thesecarboxylic acid detergents may be prepared by reacting a basic metalcompound with at least one carboxylic acid and removing free water fromthe reaction product. These compounds may be overbased to produce thedesired TBN level. Detergents made from salicylic acid are one preferredclass of detergents derived from carboxylic acids. Useful salicylatesinclude long chain alkyl salicylates. One useful family of compositionsis of the formula

where R is a hydrogen atom or an alkyl group having 1 to 30 carbonatoms, n is an integer from 1 to 4, and M is an alkaline earth metal.Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ orgreater. R may be optionally substituted with substituents that do notinterfere with the detergent's function. M is preferably, calcium,magnesium, or barium. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols bythe Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of thehydrocarbyl-substituted salicylic acids may be prepared by doubledecomposition of a metal salt in a polar solvent such as water oralcohol.

Alkaline earth metal phosphates are also used as detergents.

Detergents may be simple detergents or what is known as hybrid orcomplex detergents. The latter detergents can provide the properties oftwo detergents without the need to blend separate materials. See U.S.Pat. No. 6,034,039 for example.

Preferred detergents include calcium phenates, calcium sulfonates,calcium salicylates, magnesium phenates, magnesium sulfonates, magnesiumsalicylates and other related components (including borated detergents).Typically, the total detergent concentration is 0.01 to 6.0 wt %,preferably, 0.1 to 3.5 wt %.

Antioxidants retard the oxidative degradation of base oils duringservice. Such degradation may result in deposits on metal surfaces, thepresence of sludge, or a viscosity increase in the lubricant. Oneskilled in the art knows a wide variety of oxidation inhibitors that areuseful in lubricating oil compositions. See, Klamann in Lubricants andRelated Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197,for example.

Useful antioxidants include hindered phenols. These phenolicanti-oxidants may be ashless (metal-free) phenolic compounds or neutralor basic metal salts of certain phenolic compounds. Typical phenolicantioxidant compounds are the hindered phenolics which are the oneswhich contain a sterically hindered hydroxyl group, and these includethose derivatives of dihydroxy aryl compounds in which the hydroxylgroups are in the o- or p-position to each other. Typical phenolicantioxidants include the hindered phenols substituted with C₆+ alkylgroups and the alkylene coupled derivatives of these hindered phenols.Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol;2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol;2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol;2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecylphenol. Other useful hindered mono-phenolic antioxidants may include forexample hindered 2,6-di-alkyl-phenolic proprionic ester derivatives.Bis-phenolic antioxidants may also be advantageously used in combinationwith the instant disclosure. Examples of ortho-coupled phenols include:2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol);and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenolsinclude for example 4, 4′-bis(2,6-di-t-butyl phenol) and4,4′-methylene-bis(2,6-di-t-butyl phenol).

Non-phenolic oxidation inhibitors which may be used include aromaticamine antioxidants and these may be used either as such or incombination with phenolics. Typical examples of non-phenolicantioxidants include: alkylated and non-alkylated aromatic amines suchas aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic,aromatic or substituted aromatic group, R⁹ is an aromatic or asubstituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(X)R¹²where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is ahigher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, andpreferably contains from 6 to 12 carbon atoms. The aliphatic group is asaturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic orsubstituted aromatic groups, and the aromatic group may be a fused ringaromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joinedtogether with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of atleast 6 carbon atoms. Examples of aliphatic groups include hexyl,heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups willnot contain more than 14 carbon atoms. The general types of amineantioxidants useful in the present compositions include diphenylamines,phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenylphenylene diamines. Mixtures of two or more aromatic amines are alsouseful. Polymeric amine antioxidants can also be used. Particularexamples of aromatic amine antioxidants useful in the present disclosureinclude: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine;phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal saltsthereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. Theseantioxidants may be used individually by type or in combination with oneanother. Such additives may be used in an amount of 0.01 to 5 wt %,preferably 0.01 to 1.5 wt %, more preferably zero to less than 1.5 wt %,most preferably zero.

Conventional pour point depressants (also known as lube oil flowimprovers) may be added to the compositions of the present disclosure ifdesired. These pour point depressant may be added to lubricatingcompositions of the present disclosure to lower the minimum temperatureat which the fluid will flow or can be poured. Examples of suitable pourpoint depressants include poly-mrethacrylates, polyacrylates,polyarylamides, condensation products of haloparaffin waxes and aromaticcompounds, vinyl carboxylate polymers, and terpolymers ofdialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers.U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655,479;2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pourpoint depressants and/or the preparation thereof. Such additives may beused in an amount of 0.01 to 5 wt %, preferably 0.01 to 1.5 wt %.

Seal compatibility agents help to swell elastomeric seals by causing achemical reaction in the fluid or physical change in the elastomer.Suitable seal compatibility agents for lubricating oils include organicphosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzylphthalate, for example), and polybutenyl succinic anhydride. Suchadditives may be used in an amount of 0.01 to 3 wt %, preferably 0.01 to2 wt %.

Anti-foam agents may advantageously be added to lubricant compositions.These agents retard the formation of stable foams. Silicones and organicpolymers are typical anti-foam agents. For example, polysiloxanes, suchas silicon oil or polydimethyl siloxane, provide antifoam properties.Anti-foam agents are commercially available and may be used inconventional minor amounts along with other additives such asdemulsifiers; usually the amount of these additives combined is lessthan 1 percent and often less than 0.1 percent.

A friction modifier is any material or materials that can alter thecoefficient of friction of a surface lubricated by any lubricant orfluid containing such material(s). Friction modifiers, also known asfriction reducers, or lubricity agents or oiliness agents, and othersuch agents that change the ability of base oils, formulated lubricantcompositions, or functional fluids, to modify the coefficient offriction of a lubricated surface may be effectively used in combinationwith the base oils or lubricant compositions of the present disclosureif desired. Friction modifiers that lower the coefficient of frictionare particularly advantageous in combination with the base oils and lubecompositions of this disclosure. Friction modifiers may includemetal-containing compounds or materials as well as ashless compounds ormaterials, or mixtures thereof. Metal-containing friction modifiers mayinclude metal salts or metal-ligand complexes where the metals mayinclude alkali, alkaline earth, or transition group metals. Suchmetal-containing friction modifiers may also have low-ashcharacteristics. Transition metals may include Mo, Sb, Sn, Fe, Cu, Zn,and others. Ligands may include hydrocarbyl derivative of alcohols,polyols, glycerols, partial ester glycerols, thiols, carboxylates,carbamates, thiocarbamates, dithiocarbamates, phosphates,thiophosphates, dithiophosphates, amides, imides, amines, thiazoles,thiadiazoles, dithiazoles, diazoles, triazoles, and other polarmolecular functional groups containing effective amounts of O, N, S, orP, individually or in combination. In particular, Mo-containingcompounds can be particularly effective such as for exampleMo-dithiocarbamates, Mo(DTC), Mo-dithiophosphates, Mo(DTP), Mo-amines,Mo (Am), Mo-alcoholates, Mo-alcohol-amides, etc. See U.S. Pat. No.5,824,627; U.S. Pat. No. 6,232,276; U.S. Pat. No. 6,153,564; U.S. Pat.No. 6,143,701; U.S. Pat. No. 6,110,878; U.S. Pat. No. 5,837,657; U.S.Pat. No. 6,010,987; U.S. Pat. No. 5,906,968; U.S. Pat. No. 6,734,150;U.S. Pat. No. 6,730,638; U.S. Pat. No. 6,689,725; U.S. Pat. No.6,569,820; WO 99/66013; WO 99/47629; WO 98/26030.

Ashless friction modifiers may have also include lubricant materialsthat contain effective amounts of polar groups, for example,hydroxyl-containing hydrocarbyl base oils, glycerides, partialglycerides, glyceride derivatives, and the like. Polar groups infriction modifiers may include hydrocarbyl groups containing effectiveamounts of O, N, S, or P, individually or in combination. Other frictionmodifiers that may be particularly effective include, for example, salts(both ash-containing and ashless derivatives) of fatty acids, fattyalcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates,and comparable synthetic long-chain hydrocarbyl acids, alcohols, amides,esters, hydroxy carboxylates, and the like. In some instances fattyorganic acids, fatty amines, and sulfurized fatty acids may be used assuitable friction modifiers.

Useful concentrations of friction modifiers may range from 0.01 wt % to10-15 wt % or more, often with a preferred range of 0.1 wt % to 5 wt %.Concentrations of molybdenum-containing materials are often described interms of Mo metal concentration. Advantageous concentrations of Mo mayrange from 10 ppm to 3000 ppm or more, and often with a preferred rangeof 20-2000 ppm, and in some instances a more preferred range of 30-1000ppm. Friction modifiers of all types may be used alone or in mixtureswith the materials of this disclosure. Often mixtures of two or morefriction modifiers, or mixtures of friction modifier(s) with alternatesurface active material(s), are also desirable.

When lubricating oil compositions contain one or more of the additivesdiscussed above, the additive(s) are blended into the composition in anamount sufficient for it to perform its intended function. Typicalamounts of such additives useful in the present disclosure are shown inTable 1, below.

Note that many of the additives are shipped from the manufacturer andused with a certain amount of base oil diluent in the formulation.Accordingly, the weight amounts in the table below, as well as otheramounts mentioned in this specification, are directed to the amount ofactive ingredient (that is the non-diluent portion of the ingredient).The wt % indicated below are based on the total weight of thelubricating oil composition.

TABLE 1 Typical Amounts of Various Lubricant Oil Components ApproximateApproximate Compound wt % (Useful) wt % (Preferred) Detergent 0.01-60.01-4 Dispersant 0.1-20 0.1-8 Friction Modifier 0.01-5 0.01-1.5Viscosity Index Improver 0.0-4 0.01-4, more preferably (solid polymerbasis) 0.01-1, most preferably Antioxidant 0.1-5 0.1-1.5 Anti-wearAdditive 0.01-6 0.01-4 Pour Point Depressant 0.0-5 0.01-1.5 (PPD)Anti-foam Agent 0.001-3 0.001-0.3 Base stock or base oil Balance Balance

The foregoing additives are all commercially available materials. Theseadditives may be added independently but are usually precombined inpackages which can be obtained from suppliers of lubricant oiladditives. Additive packages with a variety of ingredients, proportionsand characteristics are available and selection of the appropriatepackage will take the requisite use of the ultimate composition intoaccount.

As will be seen from the Examples herein, the compositions of thedisclosure are sufficiently shear stable to provide stay-in-gradeperformance. Additionally, the compositions demonstrate surprising fueleconomy performance in both diesel and gasoline engines. Thus, thecompositions described herein are useful for lubricating diesel-poweredand gasoline-powered, internal combustion engines such as those used forexample in passenger vehicles, and in other classes of small enginessuch as used in lawn mowers and chain saws. They are also useful forlubricating diesel-powered engines such as those used in trucks,construction machinery and marine diesel engines.

Accordingly, an improved method for lubricating internal combustionengines is provided which comprises supplying to the engine, whenoperated, a lubricating composition of the present disclosure.

It should be understood that viscosities of the lubricant compositions,lubricating components, and basestocks are measured according toaccepted procedures. Kinematic viscosity (KY) is measured using ASTMD445, D7279, and comparable methods. High temperature high shearviscosity (1HTHS) is measured using ASTM D4683, CEC L-36, and comparablemethods. Viscosity of such materials may also be usefully characterizedas a function of temperature and shear rate, for example in thetemperature range of 60° C. to 160° C., and shear rate range of 10³sec⁻¹ to 10⁸ sec⁻¹.

EXAMPLES

The following examples further illustrate the present disclosure. Theseexamples are presented by way of illustration and are not intended tolimit the scope of the disclosure.

Example 1

A series of SAE 0W-30 diesel-type engine oils was formulated tosubstantially the same low HTHS viscosity, i.e. 3 to 3.1 mPa-s, and tosubstantially the same high HTHS viscosity, i.e. 3.4 to 3.6 mPa-s. TheVM weight ratios ranged from 0.1 to 0.5. A major base oil in eachinstance is a Group III base oil, and each lubricant composition alsocontains Group IV and Group V base oils, and the same additivescombination in substantially the same amounts. The example compositionsalong with a reference composition are shown in Table A.

TABLE A Diesel Engine Oils, SAE 0W-30 - Compositions, PropertiesLubricant Composition* Active VM Wt Base Base HTHS Ratio Active Stocks;Stocks; 10⁶ sec⁻¹, VM Types High-SSI/Low- VMs Grp III Grp IV 150° C.KV100 Example (nominal SSI) SSI (Wt %) (Wt %) (Wt %) (mPa-s) mm²/s A1Paratone 8941 0.15 1.1 75 6 3.56 12.2 (50) SV200 (4) A2 Paratone 89410.24 1.1 75 5 3.50 12.1 (50) SV200 (4) A3 Paratone 8941 0.40 1.0 75 43.47 12.0 (50) SV200 (4) B1 Paratone 8941 0.15 0.8 74 4 3.11 10.0 (50)SV200 (4) B2 Paratone 8941 0.24 0.8 74 4 3.05 10.0 (50) SV200 (4) B3Paratone 8941 0.41 0.7 74 3 3.13 10.1 (50) SV200 (4) Ref. 1 SV200 (4)0.00 1.2 80 7 3.50 12.0 *Balance of lubricant compositions includeadditives, Grp V base stock.

Example 2

A series of SAE 0W-30 gasoline-type engine oils was formulated to thesame low HTHS viscosity, i.e., 3 to 3.1 mPa-s, and to substantially thesame high HTHS viscosity, i.e., 3.4 to 3.6 mPa-s. The VM weight ratiosranged from 0.1 to 0.5. The base oil in each instance is primarily aGroup III base oil or a blend of Group III and Group IV base oils. Eachlubricant composition also contains Group V base oil (alkyl aromaticand/or ester), and substantially the same additives combinations insubstantially the same amounts. The example compositions along withreference compositions are shown in Table B.

TABLE B Gasoline Engine Oils, SAE 0W-30 - Compositions, PropertiesLubricant Composition* Active VM Base Base HTHS Wt Ratio Active Stocks;Stocks; 10⁶ sec⁻¹, VM Types High- VMs Grp III Grp IV 150° C. KV100Example (nominal SSI) SSI/Low-SSI (Wt %) (Wt %) (Wt %) (mPa-s) mm²/s C1Paratone 8941 0.14 1.2 74 6 3.53 12.2 (50) SV200 (4) C2 Paratone 89410.24 1.1 74 5 3.56 12.3 (50) SV200 (4) C3 Paratone 8941 0.40 1.0 74 43.57 12.1 (50) SV200 (4) D1 SV300 (59) 0.27 1.2 59 20 3.48 12.3 SV200(5) E1 SV140 (58) 0.31 1.3 58 21 3.52 12.4 SV200 (4) F1 Paratone 89410.15 0.8 77 4 3.12 10.1 (50) SV200 (4) F2 Paratone 8941 0.24 0.8 76 43.14 10.1 (50) SV200 (4) F3 Paratone 8941 0.41 0.7 76 3 3.10 10.2 (50)SV200 (4) G1 SV261 (20) 0.62 1.0 49 32 3.46 12.2 SV200 (4) G2 SV151 (9)0.36 1.1 48 33 3.46 12.2 SV200 (4) Ref. 2 SV200 (4) 0.00 1.2 80 7 3.5012.0 Ref. 5 SV200 (4) 0.00 1.1 46 28 3.49 12.0 *Balance of lubricantcompositions include additives, Grp V base stock.

Example 3

In this example, oil compositions A1, A2, A3 and B1 of Example 1 weretested in a passenger diesel vehicle with a start-of-test (SOT)temperature of 22° C., using the European NEDC fuel economy testprotocol. The fuel economy improvement percent, % FEI, results are shownin Table C.

TABLE C Diesel Vehicle Fuel Economy Improvement, % FEI (Mercedes BenzC250 CDI; NEDC Procedure; SOT Temp = 22° C.) Active VM Wt Ratio HTHS,10⁶ sec⁻¹ , Example High-SSI/Low-SSI 150° C. (mPa-s) % FEI Al 0.15 3.560.59 A2 0.24 3.50 1.02 A3 0.40 3.47 1.33 B1 0.15 3.11 1.59 Reference 1 03.5 ≦0.2 (Extrapolated from A1, A2, A3) Reference 3 0 3.5 0 (ZeroReference MB 225.11)

As can be seen from oils A1 to A3, the % FEI increases with increasingVM wt ratios of high-SSI/low-SSI. In Reference 1, the VM wt ratio=0,since only SV200 was used in that composition. Thus, oils A1 to A3,which each contain an effective amount of high-SSI VM, achievesignificantly higher fuel efficiency, % FEI, than that of Reference 1which contains zero high-SSI VM.

A comparison of oil B1 (HTHS viscosity of 3.11 mPa-s) with oil A1 (HTHSviscosity of 3.56 mPa-s) demonstrates that the same combination ofhigh-SSI VM and low-SSI VM will provide positive % FEI for oils havingdifferent HTHS viscosities, both low and high viscosities, respectively.

Example 4

Gasoline-type engine oil compositions C1, C3, D1 and E1 of Example 2were tested in a passenger gasoline vehicle with a start-of-test (SOT)temperature of 22° C., using the European NEDC fuel economy testprotocol. The fuel economy improvement percent, % FEI, results are shownin Table D.

TABLE D Gasoline Vehicle Fuel Economy Improvement, % FEI (Mercedes BenzC200; NEDC Procedure; SOT Temp = 22° C.) Active VM Wt Ratio HTHS, 10⁶sec⁻¹, Example High-SSI/Low-SSI 150° C. (mPa-s) % FEI Cl 0.14 3.53 0.76C3 0.40 3.57 1.36 D1 0.27 3.48 2.12 E1 0.31 3.52 1.00 Reference 2 0 3.5≦0.4 (Extrapolated from C₁, C₃) Reference 4 0 3.5 0 (Zero Reference MB225.10)

The results for oils C1 and C3 demonstrate that % FEI increases withincreasing VM wt ratio of high-SSI/low-SSI. The results for oils D1 andE1 demonstrate that different VM materials also can be used to achieve apositive % FEI result. The lubricant compositions of this Example, whicheach contain an effective amount of high-SSI VM, achieve significantlyhigher fuel efficiency, % FEI, than that of Reference 2 which containszero high-SSI VM.

Example 5

Gasoline-type engine oil compositions G1 and G2 of Example 2 were testedin a Volkswagen gasoline engine with a start-of-test (SOT) temperatureof −7° C., using the fuel economy test VW PV 1451. The fuel economyimprovement percent, % FEI, results are shown in Table E.

TABLE E Gasoline Vehicle Fuel Economy Improvement, % FEI (VW PV 1451)Active VM Wt Ratio HTHS, 10⁶ sec⁻¹, Example High-SSI/Low-SSI 150° C.(mPa-s) % FEI G1 0.62 3.46 2.6 G2 0.36 3.46 2.6 Reference 5 0 3.49 2.2Reference 6 0 3.5 0 (Zero Reference VW)

The results for oils G1 and G2 demonstrate that % FEI increases withincreasing VM wt ratio of high-SSI/low-SSI. The lubricant compositionsof this Example, which each contain an effective amount of high-SSI VM,achieve significantly higher fuel efficiency, % FEI, than that ofReference 5, which contains zero high-SSI VM, but which is otherwiseessentially identical in composition.

Example 6

The diesel-type oil compositions A1 to A3 and B1 to B3 of Example 1 weretested for shear stability using test method ASTM D7109. The KV at 100°C. after 90 cycles is shown in Table F.

TABLE F Diesel Engine Oils, SAE 0W-30 - Shear Stability Active VM WtHTHS Diesel Injector Shear Stability-D7109 Ratio 10⁶ sec⁻¹, KV100 KV100% Loss Stay-in-Grade High-SSI/Low- 150° C. (fresh oil) (90 cycles) KV100(90 (for SAE 0W-30, Example SSI (mPa-s) mm²/s mm²/s cycles) KV100 ≧9.3mm²/s A1 0.15 3.56 12.15 11.31 6.9 Yes A2 0.24 3.50 12.10 10.96 9.4 YesA3 0.40 3.47 11.97 10.52 12.1 Yes B1 0.15 3.11 9.96 9.52 4.4 Yes B2 0.243.05 10.01 9.31 7.0 Yes B3 0.41 3.13 10.05 9.13 9.2 No

Even though Example B3 contains a mixed high-SSI VM and low-SSI VM inthe inventive range of VM weight ratio, it fails to meet thestay-in-grade shear stability requirement. This clearly demonstratesthat viscosity retention and stay-in-grade shear stability represent asignificant limitation to the use of mixed VM polymers in the instantdisclosure. So stay-in-grade shear stability controls and limits theselection of VM weight ratio and VM concentrations to those compositionsthat are effective in providing improved fuel economy performance.

Example 7

Gasoline-type oil compositions C1 to C3, D1, E1 and F1 to F3 of Example2 were tested for shear stability using test method ASTM D7109. Theresults are shown in Table G.

TABLE G Gasoline Engine Oils, SAE 0W-30 - Shear Stability DieselInjector Shear Stability- Active VM Wt HTHS D7109 Ratio 10⁶ sec⁻¹, KV100KV100 % Loss Stay-in-Grade High-SSI/Low- 150° C. (fresh oil) (90 cycles)KV100 (for SAE 0W-30, Example SSI (mPa-s) mm²/s mm²/s (90 cycles) KV100≧9.3 mm²/s C1 0.14 3.53 12.20 11.37 6.8 Yes C2 0.24 3.56 12.27 11.14 9.2Yes C3 0.40 3.57 12.10 10.61 12.3 Yes D1 0.27 3.48 12.27 10.2 <17 Yes E10.31 3.52 12.35 10.1 <18 Yes F1 0.15 3.12 10.11 9.59 5.1 Yes F2 0.243.14 10.13 9.47 6.5 Yes F3 0.41 3.10 10.19 9.26 9.1 No G1 0.62 3.46 12.211.9 2.6 Yes G2 0.36 3.46 12.2 12 2 Yes

Even though Example F3 contains a mixed high-SSI VM and low-SSI VM inthe inventive range of VM weight ratio, it fails to meet thestay-in-grade shear stability requirement. This provides anotherillustration that viscosity retention and stay-in-grade shear stabilityrepresent a significant limitation to the use of mixed VM polymers inthe instant disclosure.

All patents and patent applications, test procedures (such as ASTMmethods, UL methods, and the like), and other documents cited herein arefully incorporated by reference to the extent such disclosure is notinconsistent with this disclosure and for all jurisdictions in whichsuch incorporation is permitted.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.While the illustrative embodiments of the disclosure have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of thedisclosure. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present disclosure,including all features which would be treated as equivalents thereof bythose skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference tonumerous embodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

What is claimed is:
 1. A lubricating oil composition formulated to apreselected SAE engine oil viscosity, said composition comprising: (a) amajor amount of a base oil of lubricating viscosity; and (b) a minoramount of (i) a viscosity modifier (VM) or mixtures thereof having a lowshear stability index (SSI), and (ii) a VM or mixtures thereof having anSSI greater than the VM from (i); (c) wherein the sheared kinematicviscosity at 100° C. of the composition after 90 cycles in the dieselinjector shear stability test (ASTM D7109) is equal to or greater thanthe minimum viscosity for the preselected grade before shearing; and (d)wherein the sheared viscosity (c) is less than 25% lower relative to theunsheared composition viscosity.
 2. The composition of claim 1 whereinthe VM's of (i) therein have an SSI in the range of 4 to
 12. 3. Thecomposition of claim 1 wherein the VMs of (ii) have an SSI in the rangeof 8 to 65 or higher.
 4. The composition of claim 2 wherein the VMweight ratio of VM(ii) to VM(i) is in the range of 0.01 to 1.5.
 5. Thecomposition of claim 3 wherein the VM weight ratio of VM(ii) to VM(i) isin the range of 0.05 to
 1. 6. The composition of claim 4 wherein thetotal amount of VM(i) and VM(ii) comprises from 0.1 wt % to 2.5 wt % ofthe total weight of the composition.
 7. The composition of claim 5wherein the total amount of VM(i) and VM(ii) comprises from 0.1 wt % to2.5 wt % of the total weight of the composition.
 8. The composition ofclaim 1 wherein the VMs are selected from vinylaromatic-diolefincopolymers.
 9. The composition of claim 1 wherein the VMs are selectedfrom olefin copolymers and vinylaromatic-diolefin copolymers.
 10. Thecomposition of claim 1 wherein the base oil comprises one or more baseoils selected from Group III and Group IV oils and mixtures thereof. 11.The composition of claim 1 comprising one or more lubricant additives,selected from oxidation inhibitors, dispersants, detergents, corrosioninhibitors, metal deactivators, antiwear additives, extreme pressureadditives, pour point depressants, seal compatibility agents, frictionmodifiers, defoamants and dyes.
 12. In the method of lubricating aninternal combustion engine by supplying a lubricating oil composition tothe engine, the improvement comprising supplying an SAE multigradedlubricating oil composition to the engine, said oil compositioncomprising any of the compositions of claims 1 to 11, thereby enhancingthe fuel efficiency of the engine while providing stay-in-gradeviscosity retention for stable engine performance.